1. Android.
http://www.android.com/
2. Smartphone market share.
http://www.idc.com/getdoc.jsp?containerId=prUS23503312
3. The applications number of the google play.
http://en.wikipedia.org/wiki/Google_Play
4. Google play.
https://play.google.com/store
5. Apps drain battery power.
http://www.droidforums.net/forum/droid-razr-support/216454-battery-drain.html